Material placement method and apparatus

ABSTRACT

A material placement head for dispensing and compacting a plurality of strips of a material onto a surface with a plurality of independently movable roller assemblies. Each roller assembly of the placement head comprises a compacting roller and may be rotatably and linearly moved in six-degrees of freedom independent of the other roller assemblies of the placement head. The roller assemblies may be arranged in a staggered configuration and substantially simultaneously apply the plurality of strips of the material to the surface, such that the strips of the material are applied to adjacent paths on the surface. Each compacting roller may be malleable and substantially crowned around its outer circumferential surface to provide even compaction to the strips of the material.

RELATED APPLICATIONS

The present application is continuation patent application and claimspriority benefit, with regard to all common subject matter, ofearlier-filed U.S. nonprovisional patent application titled MATERIALPLACEMENT METHOD AND APPARATUS,” Ser. No. 11/947,573, filed Nov. 29,2007. The identified earlier-filed application is hereby incorporated byreference into the present application.

BACKGROUND

1. Field

The present invention relates to structural and aerodynamic aircraftparts. More particularly, the present invention relates to materialdispensing and compaction, such as composite tape automated fiberplacement (AFP).

2. Related Art

Fiber placement is a method of compacting a resin-impregnated compositematerial, also referred to as prepreg tow, onto a surface of an itemsuch as a tool surface, mold, mandrel, or any surface used to formcomposite parts. In a typical fiber placement method, multiple layers ofthe composite material are compacted together and cured to form astrong, light-weight component of a pre-determined shape for use in theconstruction of aircrafts, missiles, satellites, automobiles, etc.

According to traditional fiber placement methods, multiple pieces ofcomposite material are typically compacted simultaneously to the surfaceusing one larger roller or segmented roller which rotates on a singleshaft. However, since the roller or roller segments rotate around asingle shaft, compacting material onto the surface over sharp angles orcomplex contours is challenging. For example, as a wide roller or asegmented roller rolls over certain complex contours, a portion of theroller makes no contact against the surface, and a portion of the tapeis not compacted. The portion of the material that is not compacted canresult in delamination or porosity of the cured part formed by thematerial.

After dispensing and compacting material onto the surface in onedirection, traditional fiber placement machines reverse directions byrotating an entire material placement head 180°. For example, in atypical application, a material placement head dispenses and compactsmaterial onto a surface in one direction, then cuts the material. Afterthis, the material placement head continues traveling a specifiedroll-off distance and then retracts from the surface. Then the materialplacement head rotates 180°, reapproaches the surface, engages thesurface, and dispenses and compacts the material to the surface,traveling in the opposite direction. Because of the many thousands ofstrands required for a typical composite part, thisretract-rotate-reapproach method can add a significant amount of time tothe material application process.

Current rollers known in the art for compacting composite material areflat from edge to edge. Therefore, in order to apply an equal amount ofpressure to an entire strip of tape during compaction, the roller mustremain perpendicular to the surface. This can be challenging orsometimes impossible to achieve depending on the complexity of thecontours required for a given part.

Accordingly, there is a need for an improved method of dispensing andcompacting material to a surface that does not suffer from the problemsand limitations of the prior art.

SUMMARY

The present invention provides an improved material placement system andmethod for dispensing and compacting material, such as prepreg tow, ontoa surface, such as a mold surface, a mandrel surface, or any surfaceused to form composite parts.

In various embodiments of the invention, the placement head comprises afirst roller supported by a base for applying a first portion of thematerial along a first path of the surface; a second roller supported bythe base for applying a second portion of the material along a secondpath of the surface; and a first actuator for moving the first rollerrelative to the base and independently of the second roller, therebyallowing both the first roller and the second roller to remain incontact with the surface as a first distance between the base and thefirst path changes relative to a second distance between the base andthe second path.

In other embodiments of the invention, the first path is substantiallyadjacent the second path, and the first actuator moves the first rollerbetween a first position closer to the base and a second positionfarther from the base. Furthermore, the first actuator may pivot thefirst roller about a first axis, and rotate the first roller about asecond axis, the second axis being substantially perpendicular to thefirst axis. The roller assemblies may be coupled to the base in asubstantially staggered configuration. Each roller assembly comprises acompaction roller and may dispense and compact a portion of the materialto a portion of the surface and is independently rotatably, pivotally,and linearly moveable in six degrees of freedom.

In embodiments of the invention, the compaction roller of the rollerassembly may be substantially crowned along its outer circumferentialsurface to more effectively dispense and compact the material to thesurface. The compacting roller may be made of a malleable material suchas rubber, allowing the crowned surface to compress against the surfaceas pressure is applied to the roller.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention is described in detail below withreference to the attached drawing figures, wherein:

FIG. 1 is an isometric view of a material placement system and aplacement head constructed in accordance with an embodiment of thepresent invention;

FIG. 2 is a perspective view of the placement head of FIG. 1 applyingstrips of a material to a surface;

FIG. 3 is an isometric view of the placement head of FIG. 1;

FIG. 4 is a plan view of the bottom of the placement head of FIG. 3;

FIG. 5 is a plan view of one side of the placement head of FIG. 3;

FIG. 6 is an isometric view of a roller assembly pair of FIG. 3 and itsactuator assembly;

FIG. 7 is an isometric view of one roller assembly pair of FIG. 3 andits actuator assembly, with one roller assembly actuated slightly higherthan the other roller assembly;

FIG. 8 is an isometric view of one roller assembly pair of FIG. 3 andits actuator assembly;

FIG. 9 is an isometric view of one roller assembly pair of FIG. 3 andits actuator assembly, illustrating the rotational motion of a rotatingactuator;

FIG. 10 is a side view of one roller assembly pair of FIG. 3 and itsactuator assembly, wherein the motion of a pivoting actuator isillustrated;

FIG. 11 is an isometric view of a roller assembly constructed inaccordance with an embodiment of the present invention;

FIG. 12 is an exploded view of the roller assembly of FIG. 11;

FIG. 13 is a fragmentary, cross-sectional, isometric view of the rollerassembly of FIG. 11, wherein a cutting mechanism is in an open position;

FIG. 14 is a fragmentary, cross-sectional, isometric view of the rollerassembly of FIG. 11, wherein the cutting mechanism is in a closedposition, thereby cutting the material;

FIG. 15 is a cross-sectional plan view of the roller assembly of FIG.11, with the material being dispensed in a first direction along asurface;

FIG. 16 is a cross-sectional plan view of the roller assembly of FIG.11, with the material being cut by the cutting mechanism;

FIG. 17 is a cross-sectional plan view of the roller assembly of FIG.11, with the material being fed to a second side of the compactingroller;

FIG. 18 is a cross-sectional plan view of the roller assembly of FIG.11, with the material being dispensed in a second direction along thesurface;

FIG. 19 is a cross-sectional view of a compacting roller constructed inaccordance with an embodiment of the present invention, wherein thecompacting roller is not biased against a surface;

FIG. 20 is a cross-sectional view of the compacting roller of FIG. 19biased against the material and the surface, with pressure applied tothe roller toward the surface; and

FIG. 21 is a cross-sectional view of the compacting roller of FIG. 19biased against the material and the surface, with enough pressureapplied to the roller toward the surface to substantially flatten anouter circumferential surface of the compacting roller.

DETAILED DESCRIPTION

FIG. 1 illustrates a material placement system 10 constructed inaccordance with an embodiment of the present invention. The materialplacement system 10 may be used for dispensing and compacting a material12, illustrated in FIG. 2, onto a surface 14 of a mold, mandrel, or anyapparatus for forming composite parts, and is particularly suited forfiber placement to construct composite parts for an aircraft. Referringto FIG. 1, the material placement system 10 may comprise a frame 16, ahead actuator 18, and a placement head 20 attached to the frame 16 andactuated by the head actuator 18.

The frame 16 may be any structure known in the art for supporting aplacement head 20, such as a gantry structure or a structure with curvedor linear axes along which the placement head 20 may be moved relativeto the frame 16 by the head actuator 18 or any other means known in theart. The head actuator 18 may be any actuator known in the art formoving an object along a frame. The head actuator 18 may move theplacement head 20 along the frame 16 linearly and rotatably.

As illustrated in FIGS. 3-4, an exemplary embodiment of the placementhead 20 comprises: a base 22, attached to the frame 16, for supportingother components; a plurality of spools 24,26,28,30,32,34,36,38 fixed tothe base 22; a plurality of actuator assemblies 40,42,44,46 fixed to thebase 22; a plurality of roller assemblies 48,50,52,54,56,58,60,62actuated by and coupled with the actuator assemblies and each comprisinga compacting roller 64,66,68,70,72,74,76,78; and a control system (notshown) for guiding the placement head 20 and independently actuating theroller assemblies to dispense and compact the material 12 onto thesurface 14.

Referring to FIGS. 2-5, the base 22 is a support to which the spools24-38 and the actuator assemblies 40-46 are fixed. The base 22 may beplanar and generally rectangular-shaped and may attach to the frame 16or any machine known in the art for moving a placement head 20 along anysurface.

The spools 24-38 are conventional and are each wound with elongatedstrips of the material 12 to be fed into at least one of the rollerassemblies 48-62, each roller assembly dispensing and compacting aplurality of lengths of the material 12 to the surface 14, asillustrated in FIG. 2. The plurality of lengths of the material 12 mayhave a width within the range of from one sixteenth of an inch to oneinch. The material 12 may be composite material, resin-impregnatedcomposite tape, slit tape tow, any material known in the art for fiberplacement, or any other formable material. In an exemplary embodiment,the spools are 18 inches long. The number of spools on the placementhead 20 may be equal to the number of roller assemblies of the placementhead 20. For example, as illustrated in FIG. 3, eight spools may feedmaterial to eight roller assemblies. Material 12 from each spool may beinserted directly into the roller assemblies or may be directed to theroller assemblies by redirect rollers (not shown) or other methods wellknown in the art.

Each of the actuator assemblies 40-46 may couple at least one or tworoller assemblies 48-62 to the base 22. Referring to FIGS. 6-10, eachactuator assembly may comprise an actuator mount 80 attached to the base22, a pivoting actuator 82 pivotally attached to the actuator mount 80,and an actuator support 84 rotatably or fixedly attached to the pivotingactuator 82. Each actuator assembly may further comprise a rotatingactuator 86 rotatably attached to the actuator support 84, a rod mount88 fixedly attached to the rotating actuator 86, and a first rod 90 anda second rod 92 slidably attached to the rod mount 88. Finally, eachactuator assembly may also comprise four rod guides 94,96,98,100, tworod guides slidably attached to the first rod 90 and two rod guidesslidably attached to the second rod 92. The first and second rods 90,92may include screw threads spiraled around an elongated outer surface ofthe rods 90,92, as illustrated in FIGS. 4-5, wherein rotational motionof the rods 90,92 allows the first and second rod 90,92 to sliderelative to the rod mount 88 or the rod guides 94-100. Although theactuator assemblies have been described with reference to theembodiments illustrated in the attached drawings, it is noted thatequivalents may be employed and substitutions made herein withoutdeparting from the scope of the invention as recited in the claims. Forexample, each actuator assembly may alternatively comprise a singleroller assembly actuator for actuating the roller assemblies.

Each of the roller assemblies 48-62 may be attached to at least one ofthe first rod 90 and the second rod 92 by the rod guides 94-100. In oneembodiment of the invention, at least one of the actuator assemblies 40may attach to a first pair of roller assemblies 48,50, as illustrated inFIGS. 6-9. Additionally, actuator assembly 42 may attach to a secondpair of roller assemblies 52,54, actuator assembly 44 may attach to athird pair of roller assemblies 56,58, and actuator assembly 46 mayattach to a fourth pair of roller assemblies 60,62. The space betweenthe compacting rollers of each roller assembly pair may be approximatelyequal to the width of a strip of the material 12, as illustrated inFIGS. 5-7. For example, the space between the compacting roller 64 andthe compacting roller 66 may be approximately equal to the width of astrip of the material 12. In one embodiment, when two roller assembliesare attached to each actuator assembly, two rod guides 94,96 may attachto one roller assembly 48 and two rod guides 98,100 may attach to theother roller assembly 50.

The actuator assemblies 40-46 may be arranged in a substantiallystaggered configuration on the base 22. Referring to FIG. 4, theactuator assemblies are staggered in a zig-zag configuration, with eachof the plurality of actuator assemblies positioned behind and to oneside of a preceding actuator assembly. The distance between any two ofthe plurality of compacting rollers of the placement head 20 may bewithin the range of from one-sixteenth of an inch to twenty inches. Inthis staggered configuration, illustrated in FIGS. 3-5, the rollerassemblies 48-62 of the placement head 20, coupled with the actuatorassemblies, dispense material 12 substantially simultaneously alongsubstantially adjacent paths on the surface 14, as illustrated in FIG.2. In various embodiments of the invention, there may be small gapsbetween the adjacent paths of material 12. Alternatively, the paths ofthe material 12 may partially overlap, with at least one edge of atleast one strip of material overlapping a portion of another strip ofmaterial.

For example, in one embodiment illustrated in FIGS. 3-5, four actuatorassemblies 40-46 each couple one of the roller assembly pairs to thebase 22. In this configuration, the first roller assembly pair 48,50 isforward of the second roller assembly pair 52,54, the second rollerassembly pair 52,54 is forward of the third roller assembly pair 56,58,and the third roller assembly pair 56,58 is forward of the fourth rollerassembly pair 60,62. The second roller assembly pair 52,54 is left ofthe first roller assembly pair 48,50, the third roller assembly pair56,58 is right of the second roller assembly pair 52,54, and the fourthroller assembly pair 60,62 is left of the third roller assembly pair56,58.

If the placement head 20 moves in a direction indicated by an arrow 110in FIG. 4, adjacent paths of the material 12 may be compacted to thesurface 14 by the following compacting rollers, listed here in orderfrom left to right: the compacting roller 68, the compacting roller 76,the compacting roller 70, the compacting roller 78, the compactingroller 64, the compacting roller 72, the compacting roller 66, and thecompacting roller 74. For example, in this configuration, one side edgeof a path of material compacted by the compacting roller 76 is adjacenta side edge of a path of material compacted by the compacting roller 68,while an other side edge of the path of material compacted by thecompacting roller 76 is adjacent a side edge of a path of materialcompacted by the compacting roller 70.

Each of the roller assemblies 48-62 may be constructed in asubstantially identical manner with substantially identical components.Referring to FIGS. 11-18, the roller assembly 50 may comprise: thecompacting roller 66 having an outer circumferential surface 112 forcompacting the material 12; a first guide element 114 with a first end116 and a second end 118 for directing the material 12 to the compactingroller 66; a second guide element 120 presenting a first guide surface122 that generally follows a first portion of the outer circumferentialsurface 112 of the compacting roller 66; and a third guide element 124presenting a second guide surface 126 that generally follows a secondportion of the outer circumferential surface 112 of the compactingroller 66.

Referring to FIGS. 11-14, the roller assembly 50 may further comprise afirst feeding roller 128 and a second feeding roller 130 forcooperatively feeding the material 12 to the first guide element 114; afourth guide element 132 for guiding the material 12 to the first andsecond feeding rollers 128,130; a cutting mechanism 134 for cutting thematerial 12; an external casing 136 enclosing the roller assembly 50components; and a guiding actuator 138, a feeding actuator 140, and acutting actuator 142 mounted to the external casing 136 for actuatingthe first guide element 114, the first and second feeding rollers128,130, and cutting mechanism 134.

Referring to FIGS. 11-12, the compacting roller 66 may comprise a firstface 144, a second face 146, a first edge 148 along the circumference ofthe first face 144, and a second edge 150 along the circumference of thesecond face 146. Additionally, the outer circumferential surface 112,interposed between the first edge 148 and the second edge 150, issubstantially crowned from the first edge 148 to the second edge 150,such that a portion of the outer circumferential surface 112 farthestfrom a rotational axis 152 of the compacting roller 66 is approximatelyhalf-way between the first edge 148 and the second edge 150. Thecompacting roller 66 is made of a substantially malleable material, suchas any kind of rubber known in the art for compacting composite materialto any surface. This allows the compacting roller 66 to engage thesurface 14 at a 90° angle or at non-90° angles, since the compactingroller 66 can conform to the surface 14 as it is pressed against thesurface 14.

For example, in FIG. 19, the compacting roller 66 is moved toward thesurface 14. When the compacting roller 66 is pressed against the surface14 at a 90° angle, the portion of the outer circumferential surface 112farthest from the rotational axis 152 of the compacting roller 66 isbiased against the material 12 and the surface 14, as illustrated inFIG. 20. Referring to FIG. 21, as additional pressure is applied, theouter circumferential surface 112 may compress until it is substantiallyflat, thereby exacting pressure first at the center of the strip of thematerial 12 and then from the center out to the side edges of the stripof the material 12, thereby evenly compacting the material 12 onto thesurface 14.

The compacting roller 66 may be any size required by a particularmaterial placement application. For example, the compacting roller 66may be between 0.01 inches and 15 inches wide. The compacting roller 66may further be between 0.1 inches and 2 inches wide. The compactingroller 66 may further be between 0.125 inches and 3 inches wide. Thecompacting roller may be wider than the strips of material 12. Forexample, a strip of material 0.25 inches wide may be applied by a rollerthat is 0.75 inches wide. The first face 144 and the second face 146 ofthe compacting roller 66 may have a diameter in the range of from about0.1 inches to about 15 inches. The first face 144 and the second face146 of the compacting roller 66 may further have a diameter in the rangeof from about 0.50 inches to about 3 inch. In an exemplary embodimentillustrated in FIG. 12, to compact a quarter-inch strip of the material12 onto the surface 14, the compacting roller 66 may have a diameter of0.750 inches and a width of 0.375 inches.

In various embodiments, the first guide element 114 is proximate thecompacting roller 66 and movable between the first position and thesecond position. In the first position, illustrated in FIGS. 15-16, thefirst end 116 of the first guide element 114 is proximate the secondguide element 120. In the second position, illustrated in FIGS. 17-18,the first end 116 of the first guide element 114 is proximate the thirdguide element 124. In one embodiment, the first guide element 114 may bepivotable about a pivot 158, whereby the first guide element 114 maypivot to the first position and to the second position. However, anymeans of moving the first guide element 114 from the first position tothe second position may be employed.

The second guide element 120 presents the first guide surface 122 thatgenerally follows a first portion of the outer circumferential surface112 of the compacting roller 66 and the third guide element 124 presentsthe second guide surface 126 that generally follows a second portion ofthe outer circumferential surface 112 of the compacting roller 66, asillustrated in FIGS. 11-12. The first portion of the outercircumferential surface 112 is generally opposed to the second portionof the outer circumferential surface 112. The second and third guideelements 120,124 may be curved in shape to direct the material 12 aroundthe compacting roller 66. Specifically, at least a portion of the secondand third guide elements 120,124 may be curved to match a portion of thecircumference of the compacting roller 66.

In various embodiments, the first feeding roller 128 is biased againstthe second feeding roller 130 with the material 12 disposedtherebetween, as illustrated in FIG. 17. When at least one of the firstand second feeding rollers 128,130 is actuated to rotate, the material12 may be cooperatively fed to the first guide element 114.Additionally, at least one of the first and second feeding rollers128,130 may be actuated to move toward and away from the other of thefirst and second feeding rollers 128,130. The fourth guide element 132may be stationary and positioned proximate the first and second feedingrollers 128,130 to guide the material 12 to the first and second feedingrollers 128,130.

Referring to FIGS. 13-14, the roller assembly 50 may also include thecutting mechanism 134 for cutting the material 12. The cutting mechanism134 may be any cutting mechanism known in the art for cutting material.In one embodiment, the cutting mechanism 134 comprises a first cuttingelement 154 and a second cutting element 156. In an open position, thefirst cutting element 154 is moved away from the second cutting element156, as illustrated in FIG. 13. The cutting mechanism 134 may generallyremain in an open position to allow the material 12 to flow through it.Referring to FIG. 14, when the material 12 requires cutting, the cuttingmechanism 134 can be closed by any means known in the art, such as thecutting actuator 142, illustrated in FIG. 11.

In various embodiments, the cutting mechanism 134, the first feedingroller 128, and the second feeding roller 130 are interposed between thefirst guide element 114 and the fourth guide element 132. Additionally,the cutting mechanism 134 may be located between the first guide element114 and the first and second feeding rollers 128,130, so that when thematerial 12 is cut, a portion of the material 12 will remain between thefirst feeding roller 128 and the second feeding roller 130.

Referring to FIGS. 11-12, the external casing 136 encloses the firstguide element 114, the cutting mechanism 134, the first feeding roller128, the second feeding roller 130, and the fourth guide element 132.The external casing 136 may also encompass a portion of the second guideelement 120, the third guide element 124, and the compacting roller 66.Furthermore, the rotational axis 152, about which the compacting roller66 rotates, may be secured to the external casing 136.

The guiding actuator 138, the feeding actuator 140, and the cuttingactuator 142 may be mounted onto the external casing 136, as illustratedin FIG. 11. For roller assembly pairs, such as the roller assemblies48,50, the guiding, feeding, and cutting actuators 138,140,142 aremounted on the external casing 136 of each roller assembly 48,50 on anexternal surface facing away from the other of the two roller assemblies48,50, as illustrated in FIGS. 8-9. The guiding actuator 138 may movethe first guide element 114 between the first position and the secondposition. The feeding actuator 140 may rotate at least one of the firstand second feeding rollers 128,130 and may move one of the first andsecond feeding rollers 128,130 toward and away from the other of thefirst and second feeding rollers 128,130. The cutting actuator 142 mayclose and open the cutting mechanism 134.

The control system of the placement head 20 may be any control systemknown in the art for sending and receiving electronic signals. Thecontrol system is programmable to communicate with any of the actuators40-46,138-142 and the roller assemblies 48-62. The control system maycontrol one of the actuator assemblies independently of another of theactuator assemblies, thereby allowing independent movement of eachroller assembly in up to six degrees of freedom, three linear and up tothree rotary. So, for example, each roller assembly may move linearly inboth directions along each of an X-axis, Y-axis, and Z-axis, androtatably about an X-axis, Y-axis, and/or Z-axis. The control system mayalso monitor each roller assembly individually for errors within thematerial 12 or the roller assembly.

In an exemplary embodiment, the control system may command one pivotingactuator 82 of the actuator assembly 40 to pivot the first rollerassembly pair 48,50 about a first axis, as illustrated in FIG. 10,independent of the other actuator assemblies 42-46. The pivotingactuator 82 may pivot the first roller assembly pair 48,50 60° forwardand 60° backward about the first axis. The control system may alsocommand the rotating actuator 86 to rotate about a second axis, asillustrated in FIG. 8-9, thereby orienting the first roller assemblypair 48,50 in a different direction than the other roller assembly pairsof the placement head 20. The first axis may be substantiallyperpendicular to the second axis.

In various embodiments, the control system may also command at least oneof the roller assemblies 48-62 to slide closer to or further from thebase 22 than at least one other roller assembly, independently of theother roller assemblies 48-62 of the placement head 20. For example, thesecond rod 92 of the first roller assembly pair 48,50 may be commandedby the control system to slide the roller assembly 50 away from the base22, thereby extending the roller assembly 50 farther away from the base22 than the roller assembly 48, as illustrated in FIGS. 6-7. Then thecontrol system may command the second rod 92 to slide the rollerassembly 50 back to a position closer to the base 22. Additionally, thecontrol system may command both rollers of the first roller assemblypair 48,50 to slide closer to or further from the base 22simultaneously.

Individual control and movement of the roller assemblies 48-62 allowsthe material 12 to be uniformly compacted onto the surface 14 moreefficiently and effectively than prior art material application methods,because the multi-directional individual freedom of movement allows theroller assemblies to better conform to tight radii and complex contoursof the surface 14. This allows continuous contact of the compactingrollers 64-78 and the material 12 with the surface 14.

A method for individual control and movement of the roller assemblies48-62 comprises: feeding a plurality of portions of the material 12through a plurality of the roller assemblies of a placement head 20;substantially simultaneously applying the plurality of portions of thematerial 12 to the surface 14 with the plurality of roller assembliessuch that the portions of the material 12 are applied to adjacent pathson the surface 14; and moving each roller assembly in six degrees offreedom independently of the other roller assemblies to dispense andcompact the material 12 to the surface 14, as illustrated in FIGS. 2-3.

For example, referring to FIGS. 6-7 the method may include moving atleast one compacting roller 66 between a position closer to a base 22 ofthe placement head 20 and a position farther from the base 22 of theplacement head 20, independently of the other compacting rollers, toapply the material 12 to the surface 14. As illustrated in FIGS. 8-10,the method may also further comprising pivoting at least one rollerassembly 50 about a first axis and rotating the same roller assembly 50about a second axis, the second axis being substantially perpendicularto the first axis.

The method may further comprise tilting at least one of the rollerassemblies 48-62 at a different angle relative to the base 22 from theother roller assemblies. The method may also further comprise tilting atleast one of the roller assemblies at non-90° angles relative to thesurface 14. Additionally, the method may comprise staggering adjacentroller assemblies 48-62 or roller assembly pairs and substantiallysimultaneously moving the roller assemblies 48-62 along adjacent pathson the surface 14.

Another method of the present invention allows the material 12 to bebidirectionally dispensed and compacted to the surface 14 with outrequiring the roller assemblies 48-62 or placement head 20 to rotate180°. The method, illustrated in FIGS. 15-18, comprises the steps ofmoving the first guide element 114 of the roller assembly 50 to thefirst position; feeding the material 12 through the first guide element114 such that the material 12 engages the second guide element 120proximate the first side of the compacting roller 66; urging thecompacting roller 66 toward the surface 14 such that the compactingroller 66 presses the material 12 against the surface 14; and moving oneof the compacting roller 66 and the surface 14 in a first directionrelative to the other of the compacting roller 66 and the surface 14,thereby dispensing and compacting the material 12 onto the surface 14along the first direction, as illustrated in FIG. 15.

The method further comprises moving the first guide element 114 to thesecond position; feeding the material 12 through the first guide element114 such that the material 12 engages the third guide element 124proximate the second side of the compacting roller 66; urging thecompacting roller 66 toward the surface 14 such that the compactingroller 66 presses the material 12 against the surface 14; and moving oneof the compacting roller 66 and the surface 14 in a second directionrelative to the other of the compacting roller 66 and the surface 14,thereby dispensing and compacting the material 12 onto the surface 14along the second direction, as illustrated in FIG. 18.

The method may further comprise biasing the first feeding roller 128 andthe second feeding roller 130 against each other, with the material 12interposed therebetween, and rotating at least one of the first feedingroller 128 and the second feeding roller 130, thereby cooperativelyfeeding the material 12 through the fourth guide element 132, the opencutting mechanism 134, the first guide element 114, and the second guideelement 120. When the material 12 engages the compacting roller 66 andthe surface 14, the first feeding roller 128 and the second feedingroller 130 may disengage the material 12 by moving at least one of thefirst feeding roller 128 and the second feeding roller 130 away from theother of the first feeding roller 128 and the second feeding roller 130.Then the material 12 may be dispensed and compacted onto the surface 14in the first direction.

Referring to FIG. 16, the method may further comprise cutting thematerial 12 with the cutting mechanism 134 when the material 12 has beencompacted to a predetermined portion of the surface 14 in the firstdirection. After the material 12 is cut, at least one of the firstfeeding roller 128 and the second feeding roller 130 may be moved towardthe other of the first feeding roller 128 and the second feeding roller130, biasing the first feeding roller 128 against the second feedingroller 130, with the material 12 interposed therebetween, as illustratedin FIG. 16. Referring to FIG. 17, the method may then involve actuatingat least one of the first feeding roller 128 and the second feedingroller 130 to rotate, causing both the first feeding roller 128 and thesecond feeding roller 130 to rotate toward each other to feed thematerial 12 through the open cutting mechanism 134, to the first guideelement 114, and then to the third guide element 124. Once the material12 engages both the compacting roller 66 and the surface 14, at leastone of the first feeding roller 128 and the second feeding roller 130may be moved away from the other of the first feeding roller 128 and thesecond feeding roller 130, thereby disengaging the material 12. Then thematerial 12 may be dispensed and compacted onto the surface 14 in thesecond direction, as illustrated in FIG. 18.

Although the invention has been described with reference to theembodiments illustrated in the attached drawings, it is noted thatequivalents may be employed and substitutions made herein withoutdeparting from the scope of the invention as recited in the claims. Forexample, in various embodiments, the roller assemblies 48-62 of theinvention described above could be replaced with any roller suitable forcompacting material 12 to any surface. Additionally, each of the rollerassemblies, compacting rollers, and actuator assemblies of the placementhead 20 may be constructed and actuated as illustrated in FIGS. 6-21.

1. A placement head for applying a material to a surface, said placementhead comprising: a base; a first roller supported by the base forapplying a first portion of the material along a first path of thesurface; a second roller supported by the base for applying a secondportion of the material along a second path of the surface; a firstactuator for moving the first roller relative to the base andindependently of the second roller, thereby allowing both the firstroller and the second roller to remain in contact with the surface as afirst distance between the base and the first path changes relative to asecond distance between the base and the second path; a third rollersupported by the base for applying a third portion of the material alonga third path of the surface; and a third actuator for moving the thirdroller relative to the base and independently of the first roller andthe second roller, wherein the first path is substantially adjacent afirst edge of the second path and the third path is substantiallyadjacent a second edge of the second path, wherein the first roller andthe third roller are located forward of the second roller.
 2. Theplacement head as set forth in claim 1, the first roller positioned suchthat a distance between the first roller and the second roller is withinthe range of from one sixteenth of an inch to twenty inches.
 3. Theplacement head as set forth in claim 1, wherein the first actuator movesthe first roller between a first position closer to the base and asecond position farther from the base, pivots the first roller about afirst axis, and rotates the first roller about a second axis, the secondaxis being substantially perpendicular to the first axis.
 4. Theplacement head as set forth in claim 1, further comprising a secondactuator for moving the second roller relative to the base andindependently of the first roller.
 5. The placement head as set forth inclaim 1, the base including a substantially planar face supporting thefirst roller and the second roller.